Radiologists find satisfaction in detecting abnormalities and making diagnoses. However, our judgement is required when we identify incidental findings, especially if the cost of workup is high and the benefit of workup may be low. The incidental thyroid nodule is a scenario in which we need to carefully consider the consequences of our report and recommendations 1.
A few facts about incidental thyroid nodules
- Incidental thyroid nodules are common whereas thyroid cancer is uncommon. 16-18% of patients will have an incidental nodule seen on CT and MRI 2,3. Only 1.6% of patients with one or more thyroid nodules will actually have thyroid cancer 4.
Costs of workup of incidental thyroid nodules add up. The 2012 Medicare reimbursement totals over $1000 for the following steps in the workup of a thyroid nodule: office consultation, diagnostic ultrasound, US guided FNA and cytopathology 5. Other costs to consider are patient anxiety, time lost and potential complications of diagnostic lobectomy.
Small thyroid cancers are typically indolent and patients may die with rather than of thyroid cancer 6,7. More than 96% of thyroid cancers are papillary and follicular cancers (well-differentiated) and have an excellent prognosis 8.
The observed incidence of thyroid cancer is increasing exponentially and has doubled in the last decade 8. Mortality has not changed significantly despite this trend which raises concern that the apparent increase in incidence is due to overdiagnosis of subclinical thyroid cancers 9.
How should we be reporting thyroid nodules on CT and MRI?
Reporting practices are highly variable among radiologists which really highlights the need for clear practice guidelines 10. Duke Radiology (NC, USA) have recently developed the Duke 3-tiered system reporting guidelines for incidental thyroid nodules on CT and MRI.
The Duke 3-tiered system guidelines have now been studied in several cohorts. The following is a summary of the findings.
- The 3-tiered system reduces FNA rate for incidental thyroid nodules by 34-46% 3,11
- The 3-tiered system captures the same proportion of thyroid cancers compared to a 1cm size cutoff 3
- Incidental thyroid cancers missed by the 3-tiered system represent 1% of all thyroid cancers having surgery and are small papillary cancers that are lower in stage 12
Dr Jenny Hoang, MBBS FRANZCR
Associate Professor of Radiology and Radiation Oncology at Duke University Medical Center in Durham NC, United States of America. Dr Hoang has published extensively on the topic of thyroid nodules and has several papers currently in press.
1. Hoang JK, Raduazo P, Yousem DM, Eastwood JD. What to do with incidental thyroid nodules on imaging? An approach for the radiologist. Semin Ultrasound CT MR 2012;33:150-157
2. Yousem DM, Huang T, Loevner LA, Langlotz CP. Clinical and economic impact of incidental thyroid lesions found with CT and MR. AJNR Am J Neuroradiol 1997;18:1423-1428
3. Nguyen XV, Choudhury KR, Eastwood JD, Lyman GH, Esclamado RM, Werner JD, Hoang JK. Incidental Thyroid Nodules on CT: Evaluation of 2 Risk-Categorization Methods for Work-Up of Nodules. AJNR Am J Neuroradiol 2013;34:1812-1817
4. Smith-Bindman R, Lebda P, Feldstein VA, Sellami D, Goldstein RB, Brasic N, Jin C, Kornak J. Risk of Thyroid Cancer Based on Thyroid Ultrasound Imaging Characteristics: Results of a Population-Based Study. JAMA Intern Med 2013
5. Centers for Medicare and Medicaid Services UDoHaHS. Physician Fee Schedule Search. http://www.cms.gov/apps/physician-fee-schedule/ (accessed December 2012).
6. Ito Y, Miyauchi A, Inoue H, Fukushima M, Kihara M, Higashiyama T, Tomoda C, Takamura Y, Kobayashi K, Miya A. An observational trial for papillary thyroid microcarcinoma in Japanese patients. World journal of surgery 2010;34:28-35
7. Harach HR, Franssila KO, Wasenius VM. Occult papillary carcinoma of the thyroid. A "normal" finding in Finland. A systematic autopsy study. Cancer 1985;56:531-538
8. Hoang JK, Roy Choudhury K, Eastwood JD, Esclamado RM, Lyman GH, Shattuck TM, Nguyen XV. An Exponential Growth in Incidence of Thyroid Cancer: Trends and Impact of CT Imaging. AJNR Am J Neuroradiol 2013
9. Davies L, Welch HG. Increasing incidence of thyroid cancer in the United States, 1973-2002. JAMA 2006;295:2164-2167
10. Hoang JK, Riofrio A, Bashir M, Kranz PG, Eastwood JD. High Variability in Radiologists’ Reporting Practices for Incidental Thyroid Nodules Detected on CT and MRI. In press. AJNR Am J Neuroradiol June 2014
11. Hobbs H, Bahl M, Nelson RC, Kranz PG, Esclamado RM, Wnuk N, Hoang JK. Incidental Thyroid Nodules Detected on Imaging: Can Workup be Reduced by Using the SRU Recommendations and the 3-Tier System? In press. AJR Am J Roentgenol Jan 2014
12. Bahl M, Sosa JA, Hobbs H, Nelson RC, Hoang JK. Incidental Thyroid Nodules Detected on Imaging: How Many Cancers Would Be Missed Using the 3-Tiered System? In. Submitted for review., 2013